The present invention relates to a reference plate, an exposure apparatus using the reference plate, a device manufacturing system, a device manufacturing method, a semiconductor manufacturing factory, and an exposure apparatus maintenance method.
Measurement precision calibration of an exposure apparatus such as baseline measurement or best focus position measurement conventionally uses a reference plate mounted on a stage. The reference plate bears reference mark patterns formed from a chromium or aluminum film on a glass for X/Y- or Z-direction measurement. These reference mark patterns are observed by a microscope using light of the same wavelength as that of exposure light.
The exposure light of the exposure apparatus is decreasing in wavelength in order to increase the resolution of a projection optical system and to expose a fine pattern.
FIG. 4 is a view for explaining a conventional reference plate. In FIG. 4, the upper views are schematic sectional views of the reference plate. Reference numeral 1 denotes a glass substrate; 2, a reference mark pattern formed from a chromium or aluminum film; and 4, a deposit on the surface of the reference mark pattern 2. The lower views show the wavelength of an observation signal.
When short-wavelength observation light from an ArF excimer laser or F2 excimer laser is used to detect the reference mark pattern 2 by a microscope using the conventional reference mark as shown in FIG. 4, long-time irradiation of illumination light deteriorates the pattern film of the reference mark pattern 2 or forms a deposit on the reference mark pattern 2. The image contrast then gradually decreases, until observation is no longer possible.
If the deposit 4 is formed on the surface of the reference mark pattern 2, as shown in FIG. 4, and decreases the contrast, the surface of the reference mark pattern 2 must be periodically cleaned. However, if a deposit 4 is formed at a step on the surface of the reference mark pattern 2, it is difficult to clean the surface.
The present invention has been made to overcome the conventional drawbacks, and has as its object to provide a long-service-life reference plate which enables stable high-precision mark detection even with short-wavelength observation light, an exposure apparatus using the reference plate, a device manufacturing system, a device manufacturing method, a semiconductor manufacturing factory, and an exposure apparatus maintenance method.
To achieve the above object, a reference plate according to the present invention has the following features. A reference plate used to irradiate a reference mark pattern with observation light, to detect the reflected light, and to obtain a position of the reference mark pattern, is provided, wherein the reference mark pattern is formed at a position where the reference mark pattern is not directly exposed to the observation light.
To achieve the above object, an exposure apparatus according to the present invention has the following features. An exposure apparatus is provided for exposing a wafer to a mask pattern, comprising reference plates having reference patterns formed at positions where the reference patterns are not directly exposed to observation light, as a mask reference plate formed on a mask stage for supporting a mask and a wafer reference plate formed on a wafer stage for supporting the wafer.
To achieve the above object, a device manufacturing method according to the present invention has the following features. A device manufacturing method comprises the steps of installing, in a semiconductor manufacturing factory, manufacturing apparatuses for performing various processing including an exposure apparatus which exposes a wafer to a mask pattern and uses reference plates having reference patterns formed at positions where the reference patterns are not directly exposed to observation light, as a mask reference plate formed on a mask stage for supporting a mask and a wafer reference plate formed on a wafer stage for supporting the wafer, and manufacturing a semiconductor device by using the manufacturing apparatuses in a plurality of processes.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.